While discussing a writer's fears even when sending book drafts to an already-procured agent, she said
We are not our books, right? Kind of?
The thing is, I am. Or rather, my books are my inside put outside.
But the good thing about that is, even if the book doesn't see the light of day, it remains a marker to a period of my life. When I hear a song I listened to while writing it, I can instantly see the desk I sat at; I know exactly the yearning in my heart that made that particular book breathe its first life.
Books-as-hearts are also a timeline of you as a writer. With just a flick, you can unfurl the drafts that came before, each one a pencil line on the door jam notching your writerly growth. The characters will still smile at you; they will not forget you.
Your books, shelved or out for query, published or rough, will hold this for you. They will hold all of this. And you'll love them for it.